Our objective is to create a biomimetic cochlea using inner ear progenitor cells on an engineered scaffold. We aim to replicate aspects of the inner ear sensory epithelium in vitro for use in drug screening and regeneration studies. This novel engineered approach will utilize substrates with mechanical and chemical cues that mimic the natural microenvironment of the basilar membrane extracellular matrix. In addition to recapitulating critical elements of the native environment, we will design a microfluidic device providing precise spatial and dose control over delivery of promoter compounds to direct the differentiation of progenitor cells into inner ear epithelial cells, resulting in hair cells and supporting cells oriented in a pattern mimicking the rows of cells on the basilar membrane. These biomimetic cochleae will be useful as a tool to study regeneration and for drug screening. This device will accelerate drug discovery and facilitate the improved use of stem cells in therapies for hearing loss. Estimates of over 10% of the U.S. population suffer from hearing loss, and this number will continue to rise with an aging population. Although significant strides have been made in understanding the cellular mechanisms of hearing loss and numerous academic and commercial researchers are working to develop treatments, therapies have not translated to the clinic. Stable, well-controlled in vitro models are lacking, and we aim to develo a tissue engineered test platform to accelerate drug discovery and regeneration studies. For testing and validation of our approach, we will optimize an engineered scaffold to encourage attachment, adhesion and differentiation of inner ear progenitor cells. A microfluidic delivery system will expose the cells to alternating regions of LY411575, a Notch inhibitor shown to induce differentiation into hair cells, and soluble jagged1, a supporting cell inducer. We have selected these as exemplary compounds due to their proven response. We will develop a cellular platform for in vitro drug testing, and we anticipate many future uses for the tool for physiological, pathological and regenerative studies. The engineered system will be capable of numerous scaffold alterations to accommodate the preferences of other cell types and enable the delivery of a broad range of compounds with unprecedented spatial, temporal, and dose control using a novel microfluidic approach. Inner ear progenitor cells are targets that have shown promise in treating hearing loss but are difficult to culture and differentiate in a controlld manner, making them the ideal demonstration of the benefits of this approach. We foresee our platform being used by researchers to better understand and treat the causes of hearing loss in humans. Thus the proposed work focuses on mouse progenitor cells, yet has direct application to the treatment of an unmet clinical need in humans. Our approach is unique in that it combines a specifically optimized engineered scaffold and a microfluidic delivery system with cochlear cell culture and manipulation that has never before been realized. An important aspect of our system is that the engineering approaches have been well-studied in other tissue types and are ideal in their tunability and control for application in the auditory field. The engineering development will be staged to allow parallel cellular studies of scaffolds and drug delivery, providing continuous feedback to guide device development. We will evaluate the biomimetic cochleae through various biochemical and physiological outcomes and explore its use as a biological tool for drug discovery and regenerative studies.